As a result of advancement of the wireless communication technologies in recent years, many kinds of wireless communication systems have been derived and applied to various circumstances. For example, in order to provide emergency communication services (e.g., to call the police, the fire station or the ambulance) or inter-group communication services in the public safety network framework, there is a need for direct communication between neighboring UEs to make communications therebetween more efficient.
According to the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) communication system specification, a device to device (D2D) UE within signal coverage of a base station can perform D2D data transmission with other D2D UEs by requesting a specific radio resource from the base station or by being informed of a radio resource that it can contend for. However, the 3GPP LTE communication system specification currently available does not plan for various scenarios that the D2D UE experiences (e.g., when the D2D UE is in a region having a poor signal strength) so as to provide a resource configuration adjustment or transmission mode adjustment mechanism.
Accordingly, an urgent need exists in the art to provide a resource configuration adjustment or transmission mode adjustment mechanism that allows a D2D UE to dynamically adjust the transmission mode automatically and allows a base station to dynamically adjust the resource configuration or to instruct the D2D UE to adjust the transmission mode.